User blog comment:Uncodify/What is your Go-To Pokemon?/@comment-32358261-20180804093654/@comment-32358261-20180805092027

Steadfast would still be the least used ability because it can act out of it and make use of the speed immediately. Lucario doesn’t have super high defences despite its good typing.

So it’s quite possible you’ll be ko’ed

Overall it’s better to have an ability like inner focus or justified since steadfast would require more predictions. Also with justified, there are many more knock off pokemon. So having a lucarionite wouldn’t be able to be dropped but justified still activates and lucario can mega

Technically you could use bullet punch or vacuum wave and even extreme speed to avoid flinch but they lack power until mega at which it won’t even have steadfast anymore.

Overall justified is the best ability for lucario (it would be better if it made lucario immune though. Sure it’s a not very effective hit but still would be great if it had that extra immunity)

Steadfast would be a better ability if it protected from flinch